AIR FUEL RATIO (A/F) SENSOR [SKYACTIV-G 2.0]

Purpose

• Detects the oxygen concentration (all-range air/fuel ratio) in the exhaust gas as basic information for mainly determining the fuel injection amount.

Function

• Detects the oxygen concentration (all-range air/fuel ratio) in the exhaust gas and sends it to the PCM as an oxygen concentration (all-range air/fuel ratio) signal.

  A/F sensor characteristic

  

• Because the A/F sensor has an output characteristics proportional to the actual air/fuel ratio, a detailed air/fuel ratio can be detected compared to using the heated oxygen sensor which detects the rich/lean of the oxygen concentration in relation to the theoretical air/fuel ratio.

Construction

• The A/F sensor is located on the exhaust manifold.

  

• The A/F sensor has an oxygen standard chamber which is always kept at 100% of oxygen concentration and an oxygen concentration detection chamber where the oxygen concentration in the exhaust gas is detected.

• A zirconia element has been adopted for the detection area of the A/F sensor.

• The zirconia element generates voltage according to the difference in oxygen concentration. Using this characteristic, the A/F sensor compares the oxygen concentration between the oxygen standard chamber (100%) and the oxygen concentration detection chamber and detects the oxygen concentration in the exhaust gas.

  

• Stable measurement of the air/fuel ratio is possible because heating by the heater is controlled and measurement is not affected by the exhaust gas temperature.

Operation

1. The PCM energizes the A/F sensor heater and activates the A/F sensor.

2. The A/F sensor compares the oxygen concentration between oxygen standard and exhaust gas and detects the oxygen concentration (all-range air/fuel ratio).

3. The A/F sensor sends the detected oxygen concentration (all-range air/fuel ratio) to the PCM as an output current value.

• The output current value increases when the oxygen concentration in the exhaust gas is high (Lean fuel).

• The output current value decreases when the oxygen concentration in the exhaust gas is low (Rich fuel).

4. The PCM control the air/fuel ratio based on the oxygen concentration (all-range air/fuel ratio) received as an output current value.

Fail-safe